Superior mesenteric artery syndrome

Superior mesenteric arterysyndrome (also known as SMA syndrome) is a rare condition first described in 1861. It occurs when the third (transverse) portion of the duodenum gets entrapped under the superior mesenteric artery. Anatomically, the duodenum passes across the abdominal aorta just below the origin of the SMA. In some cases, structural abnormalities cause the artery, which exits the aorta at a downward angle of about 45°, to experience downward traction, which pinches the duodenum between the artery and the body of the aorta. In the English-language medical literature, there are over 400 cases of SMA syndrome reported. Some researchers and physicians still doubt the syndrome's validity however.

Presentation and Clinical features
SMA syndrome is quite rare. Due to the general nature of the symptoms, it is difficult to estimate the frequency of cases in the general population. It does not seem to be more common in any particular race, but seems to strike women about twice as often as men. The syndrome usually occurs in older children and teenagers. About 3/4 of all cases occur between ages 10 and 30.

Surgical intervention is indicated when medical management fails. It is especially appropriate when a prolonged history of progressive weight loss, intestinal obstruction, or peptic ulcers is present. Duodenojejunostomy is most most often performed, and has about a 90% success. Laparoscopy is being used investigationally.

Natural course
Delay in the diagnosis of subacute or chronic SMA syndrome can result in malnutrition, dehydration, electrolyte disorders, and death. The acute form if untreated can result in dehydration and even intestinal perforation.

Prognosis
With proper conservative treatment in acute cases, and appropriate medical or surgical management in more chronic cases, the success rate in treating SMA syndrome is high. It is imperative to discover the underlying cause of the condition and treat that as well.